Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.
It is estimated that up to 2.2 million bone grafting procedures are performed annually [1]. As a result of injury or tumour resection, the loss of large quantities of bone tissue can overwhelm the body's natural bone healing capacity, leading to non-union. Together with infection, poor bone healing associated with major bone loss remain key challenges for orthopaedic medicine.
Non-union results in recurrent surgical procedures and long in-hospital stays which is challenging for both patients and surgeons [2, 3]. Two of the key causes that lead to non-union are an insufficiency of biological factors required for repair, and infection of the bone (osteomyelitis) [3, 4].
Insufficient biological factors can result from a large bone defect size, lack of biological growth factors (which can be further depleted by wound debridement) as well as damaged or reduced blood supply. Current treatments to restore osteogenic factors and an appropriate microenvironment include bone grafting [5], bone transport [6, 7], addition of growth factors and tissue engineering approaches. Nevertheless, all of these methods have limitations and there is an ongoing search for more effective agents.
WO2012/068619, WO2014/063194 and WO2014/089610 discuss utilising the structural characteristics of tropoelastin for formation of hydrogels, scaffolds and the like. These structures may then be adapted for use in therapeutic applications by attaching or seeding them with biological factors or cells that are required for therapy at a site or location where the structure is to be placed. Where therapy requires bone formation, WO2012/068619, WO2014/063194 and WO2014/089610 disclose that it is the biological factors (for example bone morphogenic proteins) or cells (osteocytes) attached to the tropoelastin-based structure that provide for the therapy.
There is a need for new approaches to bone formation in therapeutic applications.